I have a shifting problem on a bike that has a crank with a triple set of chainrings. The bike is a tandem. I have to put a great deal of effort to get it to shift into the big ring. Where should I start? Is there a simple adjustment I should look at first or should just jump right to replacing cables and housing?

Are you having a hard time downshifting on the front rings too? If so, it could be that the cables and housing are gunked up inside the housing.
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jimirings♦Jun 15 '12 at 12:31

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If cables are good and limit screws are set then an old school tweak is to take a set of needle nose and slightly bend the front of the chain guides of the derailleur inward. This will narrow the guide just enough up front that the chain will respond better to shifts, but because the back is left alone you shouldn't have chain rub issues.
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Chef FlambeJun 18 '12 at 19:34

4 Answers
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This is not uncommon with the old Shimano components. I had the same front derailleur and 105 STI 9-speed shifters and I had to really crank it to go into the larger cogs. The bike shop replaced the cabling (there wasn't much housing) and that really didn't help all that much, though I wish it did. The problem sort of fixed itself when I purchased a new bike with modern components. 2009 or later shimano 105 (shifters and derailleurs) are much, much easier to shift up through the cogs. Just push the button and it takes care of the rest. No having to push on it to get it to the next cog.

I am sorry I wish there was more I could recommend, but in my experience, there is not much you can do with that setup...

With my older Shimano setup I found that as it aged I had to adjust the limit screws on the front derailleur to allow it to travel past the correct position because it would then settle back a couple of millimetres - probably most of the cause was old cables, but some was definitely just old/worn components in the derailleur itself allowing flex.

As @bwalk2895 mentioned, it is an age thing - you can hold it off by tweaking (and in fact mine was much older and was still usable when I finally retired it for a new bike) but changing cables is relatively simple and should help a bit.

First off, of course, lubricate the cables and assure that the derailers are properly adjusted.

After that, make sure you're not cross-chaining too much when shifting up -- you should have your rear near the outer cog before up-shifting the front, so that the angle of the chain isn't fighting you. Also, understand that you must let up a hair on the cranks when up-shifting the front -- don't do it under full load.

But if not that then likely the rings are worn out. Even if the chain and rings gauge out OK (did you check them??) the ramps on the side of the big ring may be worn to the point that they're no longer effective.

Check the high limit screw first. If that doesn't do it, you probably want to play around with the indexing adjustment (possibly needs some tension due to cable stretch over time). It's not going to hurt if you lube the existing cables as well.

Due to the age of the cabling, it's not a bad idea to replace it anyway, but that means adjusting everything from scratch. If you're not really qualified to do that yourself, just take it to a shop and ask them to do it for you and safe yourself the time. It's not terribly difficult to learn, but it definitely takes a certain touch to get right.
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BenzoJun 17 '12 at 5:20